4.2.1.2 Limitations

This application note demonstrates that a complex task can be performed using a device with limited memory, such as the ATtiny817. However, this implementation does have some limitations.

Data Portability

The data representing the recorded digital voice signal cannot be easily read by a PC. Even though it is stored on an SD card, there is no file system used, so the data is stored in a raw format without a structure readable by typical PC software.

Power Stability

The SD card used to store data may enter an undefined state if its power source goes below a certain level (also relevant when power toggles). This will result in the SD card responding correctly during initialization and when writing data, however, it may cause an error when trying to perform a Read operation. This requires the card to be removed from the slot and re-inserted, triggering a reinitialization. Read can then be performed correctly. This state is indicated by a record operation performing correctly, followed by a playback with no sound and a periodic flash of the LED. After the SD card has been removed and reinserted, the playback button should be pressed again, at which time the recorded data can be played back successfully.